The program is evaluating blood viscosity associated variables (apparent blood viscosity at various rates of shear, hematocrit, red cell deformability, fluidity and size, degree of cellular aggregation, plasma viscosity, serum protein profile and the surface charge of the blood cellular elements) as diagnostic and prognostic indices for diseases related to or produced by altered blood flow or arising from traumatic surgical procedures. The degree of correlation between the pertinent variables is being assessed in order to develop the relevant set of measurements required for a hemorheological profile on blood samples. Subjects and patients are being divided into groups on the basis of sex, disease and surgical procedures such as elective total knee replacement, These groups will be subjected to statistical analysis which will provide a readily accessible summary of the acquired data base and provide a means of surveying how well the various measurements discriminate between the groups of subjects and patients. The classification of normal subjects is based upon the blood chemistry profile and hematological indices of the blood as well as the usual clinical assessment of the volunteer as being normal. Studies are in progress on patients with hyperviscosity syndromes, peripheral vascular disease and multiple sclerosis. Patients with myeloma and peripheral vascular disease display a higher apparent blood viscosity over the entire range of shear rates compared with the control group at equivalent hematocrit. Women on oral contraceptives have small but significant increases in apparent blood viscosity at low rates of shear over the female control group. The knee replacement surgery patients show marked increases in ESR, fibrinogen and apparent blood viscosity for hematocrits equivalent to the preoperative values. Evidence is accumulating that blood viscosity related factors will be useful for monitoring the course of diseases, improving diagnosis and suggesting manipulations to alleviate some of the clinical problems associated with the impairment of blood flow.